diff --git a/GitHubClient.py b/GitHubClient.py
index fa5453b..5513f9d 100644
--- a/GitHubClient.py
+++ b/GitHubClient.py
@@ -9,6 +9,8 @@ class GitHubClient(object):
 
     def __init__(self):
         self.github_url = os.getenv('INPUT_GITHUB_URL')
+        if not self.github_url:
+            raise EnvironmentError
         self.base_url = f'{self.github_url}/'
         self.repos_url = f'{self.base_url}repos/'
         self.repo = os.getenv('INPUT_REPO')
diff --git a/LocalClient.py b/LocalClient.py
new file mode 100644
index 0000000..9d0b606
--- /dev/null
+++ b/LocalClient.py
@@ -0,0 +1,16 @@
+import subprocess
+
+class LocalClient(object):
+    def __init__(self):
+        self.diff_url = None
+        self.commits = ['placeholder'] # content doesn't matter, just length
+        self.insert_issue_urls = False
+
+    def get_last_diff(self):
+        return subprocess.run(['git', 'diff', 'HEAD^..HEAD'], stdout=subprocess.PIPE).stdout.decode('utf-8')
+
+    def create_issue(self, issue):
+        return [201, None]
+
+    def close_issue(self, issue):
+        return 200
diff --git a/main.py b/main.py
index 28d2242..dd1d7c6 100644
--- a/main.py
+++ b/main.py
@@ -11,12 +11,21 @@ import operator
 from collections import defaultdict
 from TodoParser import *
 from LineStatus import *
+from LocalClient import *
 from GitHubClient import *
 
 
 if __name__ == "__main__":
-    # Create a basic client for communicating with GitHub, automatically initialised with environment variables.
-    client = GitHubClient()
+    # Try to create a basic client for communicating with the remote version control server, automatically initialised with environment variables.
+    try:
+        # try to build a GitHub client
+        client = GitHubClient()
+    except EnvironmentError:
+        # don't immediately give up
+        client = None
+    # if needed, fall back to using a local client for testing
+    client = client or LocalClient()
+
     # Check to see if the workflow has been run manually.
     # If so, adjust the client SHA and diff URL to use the manually supplied inputs.
     manual_commit_ref = os.getenv('MANUAL_COMMIT_REF')